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Part I By Debra Allen PhD., University of Delaware, Problem-based Learning Clearinghouse Modifications by John S. Peters, College of Charleston |
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John H. Martin,
then director of the
Moss Landing Marine Laboratories in California, suggested that we could
lessen the threat of global warming by dumping iron into the waters off
Antarctica. "Give me half a tanker of iron and I'll give you an Ice
Age,"
he (only half-jokingly) remarked during a lecture before an audience of
scientists at the Woods Hole Oceanographic Institute in 1988. Martin
proposed
that by spiking the Southern Ocean with 300,000 tons of iron, we could
remove about two billion tons of carbon dioxide from the
atmosphere.
Why iron? The
origin of the "Geritol
solution," as Martin's scheme later came to be known, is rooted in a
longstanding
speculation among biogeochemists. They wondered why the so-called HNLC
(high-nutrient, low chlorophyll) waters or "desolate zones" of the
Southern
ocean around Antarctica and of the equatorial and subarctic Pacific are
so barren (low in biological productivity), despite their seeming
abundance
of nutrients. Martin pieced together information about the
sources and
distribution of iron in open ocean waters and iron's solubility in
water,
and proposed that a low iron concentration limits productivity in these
otherwise fertile areas.
Development of a
way to measure the
minuscule amounts of iron present in seawater led to a series of "iron
in a bottle" experiments designed to test the basic premise of this
iron
availability hypothesis. The results of the first of these experiments
showed that the amount of chlorophyll found in ocean water samples
collected
from the Gulf of Alaska could be increased up to nine-fold by the
addition
of iron. A repeat of this iron seeding experiment with water samples
collected
from a few hundred miles off the Antarctic coast showed that for every
unit of iron added to the seawater, the organic carbon content of the
water
increased by a factor of 10,000.
When prominent skeptics were
reluctant
to accept these experiments, Martin (now referred to by some as
"Johnny
Ironseed" or the "Iron Man"), proposed to fertilize a test plot of the
open ocean with iron. What would happen?